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104 Cards in this Set
- Front
- Back
Evolution
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Changes in the genetic characteristics of a population over time (esp. allele frequencies)
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Population
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group of individuals of the same species living in the same area at the same time
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Common ancestry
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Relates all species to a previous species
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Descent with Modification (Process)
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Characteristics of species are modified from generation to generation (Pattern)
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LUCA
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last universal common ancestor (Hypothetical species that all species trace their ancestry back to)
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Tree of Life
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family tree of organisms that describes genealogical relationships among species with a single ancestral species at its base
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Speciation
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natural selection causing populations of one species to diverge to form new species
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Phylogeny
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actual genealogical relationships among all organisms (ex: family, ancestors, etc.)
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3 Major domains
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Eukarya, Bacteria, Archaea
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Scientific Method
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Principles and procedures for the systematic pursuit of knowledge involving the recognition and formulation of a problem, collection of data through observation and experiment, and the formulation and testing of hypotheses
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Heritable traits
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Traits passed on to offspring
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Darwin's Four Postulates
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1. Variation exists
2. Certain traits are heritable 3. More offspring produced than can survive 4. Individuals with certain traits more likely to survive |
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3 Requirements for Natural Selection to Operate
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1. Variability
2. Heritability 3. Differential Reproduction |
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Cell Theory
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All organisms are made up of cells and all cells come from existing cells
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Theory (2 components?)
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Explanation for a very general class of phenomena or observations
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Darwin's Book
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On the Origin of Species by Means of Natural Selection
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Typological thinking
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Perfect and unchanging - fixed for all time
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Population Thinking
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Variation among individuals in a population key to understanding nature of species
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Transmutation
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Species changing over time
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Acquired Traits
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Acquired characteristics that could be passed off to offspring
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Strata
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Layers of rock sediment
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Natural Selection
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Process by which individuals with certain heritable traits tend to produce more surviving offspring than do individuals without those traits, often leading to a change in the genetic makeup of the population
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Homologous Structures
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different functions but are structurally similar because of common ancestry
(Ex: limbs vs. wings) |
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Analogous structures
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similar function served and structurally similar due to convergent evolution, but not derived from a common ancestry
(Ex: birds and bats both fly but no common ancestor with that ability) |
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Vestigial structures
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remnants of features that served important functions in an organism's ancestors
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transitional feature
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trait in a fossil species that is intermediate between those of older and younger species
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Comparative embryology (Developmental homology)
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comparisons of early stages of development among organisms
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Genetic homology
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comparisons of DNA sequences and genetic traits
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Structural homology
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Similarity in adult morphology
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Acclimation
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individual phenotype changes in response to environment (changes are not passed on)
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Adaptation
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allele frequencies in a population change in response to natural selection
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Darwinian Fitness
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an organism's ability to reproduce surviving offspring
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Genetic Variation
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# and relative frequency of alleles that are present in a particular population
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Gene pool
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total collection of genes in a population at any one time
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Four Mechanisms of Evolution that shift allele frequencies
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Natural selection, genetic drift, gene flow, mutations
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Directional selection
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pattern of natural selection that favors one extreme phenotype with the result that the average phenotype of a population changes in one direction. generally reduces overall genetic variation
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Disruptive Selection
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pattern of natural selection that favors extreme phenotypes at both ends of the range of phenotypic variation. Maintains overall genetic variation
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Purifying selection
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disadvantageous alleles decline in frequency
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"Fixed" Allele
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an allele that remains in the gene pool because all members are homozygous for that allele
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Stabilizing Selection
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Pattern of natural selection that favors phenotypes near the middle of the range of phenotypic variation. Reduces overall genetic variation.
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Heterozygote Advantage
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Higher fitness than homozygous, thus maintain genetic variation in the population
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Balancing selection
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A pattern of natural selection in which no single allele is favored in all populations of a species at all times. Balance among alleles in terms of fitness and frequency.
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Frequency-dependent selection
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A pattern of selection in which certain alleles are favored only when they are rare, form of balancing selection.
Genetic variation is maintained or increased |
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Genetic Drift
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any change in allele frequencies in a population due to chance, random with respect to fitness
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Population bottleneck
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loss of genetic diversity when # of individuals is greatly reduced, causes genetic drift by limiting population size
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Founder effects
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few individuals colonize a new habitat
(Ex: Amish rate of polydactyly very high) |
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Gene flow
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Movement of individuals from one population to another
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Mutation
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restores genetic diversity by creating new alleles, causes random changes in genes
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Deleterious alleles
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alleles that lower fitness
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Artificial Selection
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changes in populations occur when humans select which individuals will produce the most offspring
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Hardy-Weinberg model
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Assumes population will not change overtime, used to study actual populations
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Hardy-Weinberg Principle
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Principle of population genetics that states that genotype frequencies in a large population do not change from generation to generation in the absence of evolutionary processes
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5 conditions of a population remaining in equilibrium
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Large Population, No migration, No net mutations, Random mating, no natural selection
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P+q =
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1
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Frequency of AA genotype
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p^2
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Frequency of aa genotype
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q^2
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Frequency of Aa genotype
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2pq
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Inbreeding Depression
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decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population
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Inbreeding
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Mating between two individuals that share a very close common ancestor - leads to loss of genotypes, NOT alleles
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Fundamental asymmetry of sex
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eggs expensive, sperm cheap (females invest more in their offspring than do males)
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Sexual Selection
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Type of natural selection that violates random mating, individuals differ in their ability to attract mates
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Mate Choice
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Females are choosy about their mates, AKA intersexual selection
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Sexual Dimorphism
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Sexual traits of males much more exaggerated than females as a result of intrasexual selection
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Intrasexual selection
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direct competition between members of the same sex for mates of the opposite sex
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Microevolution
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change in alleles over time, from one generation to the next
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Macroevolution
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creation of a new gene pool
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Speciation
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When one species splits into two or more species
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Species
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evolutionarily independent population or group of populations
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Biological species concept
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defines species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring
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Reproductive isolation
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Prevents members of different species from mating with each other
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Prezygotic isolation
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individuals of different species are prevented from mating
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Postzygotic Isolation
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hybrid offspring has low fitness and does not survive or produce offspring
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Hybrid viability
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Ability for hybrid offspring to survive
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Hybdrid fertility
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Ability for hybrid offspring to be fertile
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Morphospecies concept
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identifies evolutionary independent lineages by differences in morphology
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Phylogenetic Species concept
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reconstructing the evolutionary history of populations with monophyletic groups
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Monophyletic group (clade)
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ancestral population plus all of its descendants and just its descendants
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Synapomorphies
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homologous traits inherited from a common ancestor that are unique to certain populations or lineages
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Phylogenic species
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Smalles identifiable group with synapomorphy
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Subspecies
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populations that live in discrete geographic areas and have their own identifying traits but are not distinct enough to be considered a separate species
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Allopatric speciation
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speciation that begins with physical isolation
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Dispersal
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Colonization of a new habitat and forming a new population
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Vicariance
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physical barrier splits a widespread population into subgroups that are physically isolated
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Sympatric speciation
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speciation occurring amongst populations that occupy the same location
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Polyploidiation
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genetic isolation is created by formation of polyploidy individuals that can only breed with eachother
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Autopolyploid (intraspecific)
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Formation of different # of chromosomes due to mutation
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Allopolyploid (interspecific)
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Formation of different # of chromosomes due to different species mating
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Fusion
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Erasing distinctions between two isolated populations caused by gene flow
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Reinforcement
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Natural selection for traits that isolate populations reproductively - leads to speciation
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Hybdridization
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Leads to extinction or possibly origination of a new species by mixing two independent populations
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Phylogeny
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evolutionary history of a group of organisms
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Branch
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population through time
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node
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point in time when an ancestral species split into two descendent species
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Tip (terminal node)
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a group that is living today or ended in extinction
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Phenetic estimation
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using computer modeling and statistics to summarize similarity among populations
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Cladistic estimation
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Using parsimony to summarize similarity among populations
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Parsimony
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A principle of logic stating that the most likely explanation or pattern is the one that implies the least amount of change
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Homology
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Traits are similar due to common ancestors
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Homoplasy
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traits are similar for reasons other than common ancestry
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Ancestral trait
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characteristic that existed in an ancestor
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Derived trait
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a characteristic that is a modified form of an ancestral trait that exists today (Ex: HOX genes)
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Outgroup
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species or group that is closely related to the monophyletic group but not part of it
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Adaptive radiation
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rapid speciation in a single lineage is followed by divergence into many different adaptive forms
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3 Hallmarks of adaptive radiation
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1. Monophyletic group 2. speciation is rapid 3. species diversify ecologically
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